In the conventional green sand molding process, sand, 5-6% by weight (all mixture percentages hereinafter shall mean by weight unless specifically noted otherwise) clay, about 1-2% cereal, about 2-5% water and a 4-5% lustrous carbon producing material (such as seacoal, No-col, etc.) are mixed together to form a moldable material. The lustrous carbon material contains 30-35% volatile organic compounds with about 58% fixed carbon, 7% ash, 1% sulfur and some water. No-col contains about 25% organic material and the remainder clay. In each of these lustrous carbon producing materials the organic materials play an important role because they form a soot which prevents surface defects of the casting caused by micropores and cracks in the mold surface.
The prepared sand mixture is typically transferred to a mold line where it is placed into the bottom half of the mold and an impression of the part to be produced is made in the sand. A similar procedure is followed with the top half of the mold. A pour basin and sprue is also defined in the mold parts (halves) which communicate with the impression or mold cavity. The two halves are placed together with the pouring basin on the top for receiving molten metal. Other pin holes may be punched in the top half to facilitate a limited amount of gas venting during the casting operation, such holes being no greater in diameter than 0.125 inches. Molten metal is then poured into the basin, through the sprue and into the mold cavity to take the shape of the impression in the mold. When the hot metal is poured into the mold, there is combustion of the organic material in the mold sand as well as in the cores, until the air supply is depleted, then volatilization and partial breakdown of such organic material occurs. The gases formed as a result of such volatilization are quite odorous and some escape from the mold through said vent holes and some escape when the mold is opened to remove the casting. These gases are objectionable not only to the in-plant personnel, but to others in the environment to which the gases are exhausted outside of the plant.
The prior art has attempted to solve only the in-plant personnel problem by quickly collecting the gases such as by vacuum devices which gather the gases rapidly during the molding operation and transmit such gases to baghouses and other exhausting apparatus. However, such attempts do not solve the problem of eliminating the odors which eventually find their way into the surrounding environment; there is increasing concern by governmental agencies which prohibit such gas dumping. What is needed is a mechanism or process by which such odorous gases (containing unburned hydrocarbon from the lustrous carbon producing material) can be substantially eliminated, not merely collected or masked.